Effects of dopamine on haemodynamics and myocardial energetics in man: comparison with effects of isoprenaline and L-noradrenaline.

The effects of dopamine (DOPA) on haemodynamics, coronary blood flow and myocardial oxygen requirements were compared with those of L-noradrenaline and isoprenaline (isoproterenol) in patients after open-heart surgery, performed because of mitral valvular and congenital heart disease. The patients were in low cardiac output state but not in shock. DOPA increased heart rate less than isoprenaline, averaging 22 and 31 beats/min, and was less arrhythmogenic. DOPA increased mean arterial pressure by an average of 7 mmHg, whereas isoprenaline had little effect; noradrenaline uniformly increased all measurements of arterial pressure. DOPA and isoprenaline increased cardiac index by an average of 1.01 and 0.94 1 min--1 m--2; noradrenaline did not significantly improve peripheral perfusion. DOPA and isoprenaline decreased systemic vascular resistance by an average of 465 and 549 dynes s cm--5; noradrenaline increased resistance in all patients. For similar cardiac outputs average urine flow increased more with DOPA (75 ml/h) than with isoprenaline (28 ml/h). DOPA increased coronary blood flow and myocardial O2 consumption by an average of 28 and 3.60 ml min--1 100 g--1, noradrenaline by 16 and 1.93 and isoprenaline by 62 and 4.25 ml min--1 100 g--1 respectively. Arterial--coronary sinus O2 differences remained unchanged (normal) with DOPA and noradrenaline and decreased with isoprenaline on average by 1.10 ml/100 ml. Myocardial lactate utilization was normal before and during catecholamine administration. It is concluded that, in its haemodynamic effects, DOPA is intermediate between noradrenaline and isoprenaline. The effects of DOPA on coronary blood flow and myocardial O2 consumption are closer to those of noradrenaline than of isoprenaline. DOPA increase coronary blood flow according to myocardial metabolic demand; it is not a potent primary coronary vasodilator. DOPA, although increasing myocardial O2 consumption more than noradrenaline, is by far less O2-demanding than isoprenaline. DOPA appears to be the superior vasoactive agent among the three catecholamines for the treatment of low cardiac output state in patients with preserved coronary reserve.